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When you feed your dog, you may not know what's in his food. Perhaps the bag says "all natural" or "organic," but aside from that, you're not sure of the ingredients. All you know is that your pup seems to like it. You've never thought about whether or not the right ingredients for his diet are in the food; you just assumed the dog food companies know best.

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But are dogs really supposed to eat this kind of food? Are they happy with eating both plants and animals, just like humans? Or are they only supposed to eat animals, because they are truly carnivores?

The traditional teaching is that dogs are omnivores. However, there is some evidence that shows that dogs may be carnivores instead.

Dogs as omnivores

Biologically, dogs have an intestine size that falls in between the length of a carnivore's and an herbivore's. A dog's intestine size is a little larger than a cat's, which would lead scientists to believe they are omnivores. Dogs' ancestors, wolves, ate grains; they would binge on the grains they would discover in the stomachs of their prey. Dogs also have three genes for glucose and starch digestion, which means that they can comfortably eat vegetation and grains.

Though there is strong proof that dogs are inherently omnivores, over the past few years there has been chatter in the scientific community that dogs may in fact be carnivores.

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Dogs as carnivores

Dr. Wouter Hendriks, of Utrecht University's veterinary school, posed the idea that dogs may in fact be carnivores, not omnivores. This is because they have a low coefficient of fermentation, which is the ability to ferment and extract nutrition from plant matter. Herbivores have a high coefficient of fermentation.

According to Dr. Hendriks, it is a myth that wolves feed on the contents of their prey's stomachs. In fact, they forage very little. Some other evidence that proves dogs are carnivorous is that they have teeth for chewing bones and tearing muscle, they dig and hide their meals for future consumption like wolves and they are able to go for long periods of time without food like mammalian carnivores.

What should you feed
your pup?

Though the facts point to dogs being truly carnivorous creatures, they have been so domesticated over the past 15,000 years that they have adapted to diets including grains and plants. According to Dr. Roger Welton, the president of Maybeck Animal Hospital, eating only protein could be detrimental to your dog's health.

This is because protein metabolism generates ammonia, which is filtered out and detoxified by your dog's liver and kidneys. Overtime, the kidneys and liver will become overwhelmed if they constantly have to detoxify the meat, and your dog could end up getting cirrhosis of the liver or chronic renal failure in the kidneys. Dr. Welton recommends keeping your dog's daily protein intake at 25% (or less) of his total daily nutrient intake.

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If you want to ensure your dog is getting all the nutrients he needs, look for a high-quality brand of dog food that doesn't have things like cancer-causing chemical preservatives, anonymous meat or high-risk coloring agents. Be aware of dog food recalls and sign up to receive alerts so you know if a product is dangerous to your dog.

Of course, it is always best to ask your veterinarian for advice on the best dog food. Your vet will be able to tell you what brands of dog food are best, whether or not you should be getting senior food and what kind of food works best for your dog's breed. After all, some breeds are more sensitive to food than others.